Japanese era name
The system on which the Japanese era names are based originated in China in 140 BC, and was adopted by Japan in 645 AD, during the reign of Emperor Kōtoku.
The vast majority of Japanese Era Names were used for less than 10 years, with two being used for less than a year. Only 28 have been used for more than 10 years and less than 30 years. Only Heisei, Oei, Meiji, and Showa have been used for more than 30 years.
Certain calendar libraries support the conversion from and to the era system, as well as rendering of dates using it.